Fluid mass gyroscope



June 23, 1970 J. F. VANDREY ETAL 3,516,280

FLUID MASS GYROSCOPE Filed May 4, 1967 2 Sheets-Sheet 1 PICKOFF SYSTEM XEIQFJ 1 32 96 H644 I I I 46 m 26 IN [I4 0 V FIG. 2 INVENTORS WILLIAM L. BRYANT J. FRIEDRICH VANDREY ATTORNEY June 23, 1970 J. F. VANDREY ETAL 3,516,280

' FLUID MASS GYROSCQPE Filed May 4, 1967 2 Sheets-Sheet 2 26 24 46 34 so so 6 28 I f 40 44v H 62 I5 2 um a 0 74 (I0 FIG. 3

0 90 66 38 Z: 23 I" 7 2 Y INVENTORS LIAM L. BRYANT J. EDRICH VANDREY BY%JO/W ATTORNEY Patented June 23, 1970 3,516,280 FLUID MASS GYROSCOPE Julius Friedrich Vandrey, Perry Hall, and William L.

Bryant, Bel Air, Md., assignors to Martin-Marietta Corporation, New York, N.Y., a corporation of Maryland Filed May 4, 1967, Ser. No. 636,162 Int. Cl. G01c 19/12 US. Cl. 745.7 11 Claims ABSTRACT OF THE DISCLOSURE A gyroscopic device utilizing a spinning fluid mass. The fluid is caused to rotate within a submerged hollow, neutrally buoyant torus having its inside periphery slotted so as to allow for input and output fluid flow. Fluid jet nozzles, supported independently of the torus, are located such that their fluid output flo-w is directed tangentially along the annular interior cavity of the torus to create the spinning fluid mass and requisite angular momentum.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to gyroscopes utilizing a spinning fluid mass and, more particularly, to a gyro wherein the effect of a rotating mass is accomplished by driving a fluid around an open submerged annular raceway.

Description of the prior art Gyroscopic devices have been utilized extensively in the field of naxigational information instrumentation and are now finding extensive application within vehicle stabilization schemes or vehicle control systems. Particularly as a result of the continuing definement and technical sophistication evidenced in the latter fields, there exists a demand for gyroscopic devices having the quality of high accuracy but which are of rugged and compact design. Conventional gyroscopes, characterized in having a solid spinning mass, retain a dominant position in present markets. However, gyros substituting a fluid mass for the solid mass hold promise for supplanting the solid mass variety in an increasing number of applications.

The refined operational requirements imposed upon industry for highly sensitive and accurate gyro assemblies have necessitated the introduction of extreme care in the manufacture of conventional solid mass gyros. Special attention is required in fabricating mechanical bearing and gimbal structures to provide requisite close tolerances between their components. Ideally, a gyro is exactly balanced about its inner and outer axes, whereby the center of gravity intersects the inner axis, and no misalignment torque is encountered during stable rotation. In practice, however, such a condition is difficult to attain and spurious, unwanted torques often develop. A minor misalignment of parts or a minute amount of dirt may well lead to dynamic unbalance of the rotatable mass and consequent shortened operational life span. The increasing possibilities of defect introduction during fabrication have led to the more frequent specification by users of higher cost, ultra-clean assembly techniques and very limited part interface tolerances.

Ideally, also, the solid rotor gyro structure has spring constants which are isostatic or equal in all directions. However, in practice this is not the case and resultant errors are often in evidence. Moreover, inasmuch as a typical solid rotor device is generally operated from a voltage supply, a careful regulation of this supply is a requisite to accurate rotational speed.

Upon being precisely assembled and mounted, it is also imperative that conventional gyro equipment not be subjected to hard jars or excessive vibration; otherwise, rotor supporting bearings or gimbal mount alignments will deteriorate rapidly, leading to unacceptably inaccurate signal outputs. The increasingly severe vibration and shocks encountered in modern application, accordingly, have led to the use of undesirably complex, heavy and expensive shock prevention mounting schemes.

Fabricated in most instances from metal, the spinning mass rotors of conventional gyroscopes are often subjected to error-inducing spurious torques brought about by the influence of ambient magnetic fields, either casually encountered or derived from contiguous electrical equipment. It is, therefore, sometimes necessary to provide shielding around the gyro mounting, often thereby incurring undesired weight and space penalties.

Gyroscopes, particularly of the rate-gyro variety, characterized in having a restricted gimbal free to rotate about one axis only, having been proposed in which the rotating mass is a fluid constrained and caused to flow in circular fashion about an annular path. For applications requiring more than a momentary time span of operation, it has heretofore been the practice to envelope the spinning fluid within a closed annular raceway or torus which is in turn mounted upon an inertial platform. Motive power for causing a continual fluid spin has been derived from externally mounted electromagnetic flux developing or magneto-hydrodynamic devices usually surrounding one portion of the raceway. Such arrangements eliminate the need for the central support of a flywheel and the bearing structures attendant to such support. In addition to the elimination of friction bearing surfaces which are prone to wear out, it will be apparent that the fluid mass rate gyro requires no gimbals for suspension. The number of close tolerance components required in fabrication is considerably reduced. The life expectancy of the device is sometimes enhanced. Ultraclean assembly techniques generally are of lesser scope and manufacturing costs may be reduced, depending upon the intricacy of the fluid mass driving assembly.

In order to impart a rotary motion or spin to the fluid within the gyros, however, the fluid itself must be capable of reacting to the imposed flux of the driving device. As a result, the gyros are restricted to use with electrically conductive fluids, some of which may be corrosive in nature. The conducting fluids, such as mercury, also suffer the disadvantages of being sensitive to random or casually encountered ambient electric fields and of having densities which may be detrimental in systems Where lower component weights are desired. Weight and balance problems are also encountered upon mounting a relatively heavy or bulksome fluid spinning electromotive device over a portion of the swiveled raceway. Further, it has in the past been found necessary to provide extraneous cooling arrangements for the purpose of dissipating heat generated by wall friction developed between a liquid metal spinning fluid and the annular raceways confining it.

Additional expense contributing complexities are present in both solid rotor and fluid rotor gyros with regard to the provision of suitable damping means for minimizing spurious torques. For instance, in some designs an adjustable springing arrangement is attached to the gimbal structure to impose a damping action, while in other approaches, the gimbals are floated upon a confined fluid which serves to dissipate the torques.

As may be evidenced from the above discussion, fluid spinning mass rate gyros have thus far contributed the advantage of minimizing the requirements for close manufacturing tolerances and highly specialized fabrication techniques. Their operation without supporting rotational bearings and gimbal assemblies has also contributed to interest in their use. To the present, however,

the advantages of the fluid mass rate gyro have been in many instances outweighed by their limitations. The aforesaid limitations have been particularly apparent with regard to the methods and means thus far devised for causing the fluid mass to spin within its confining raceway. This problem has not only necessitated the use of undesirably heavy aud sometimes corrosive fluids, but also the use of bulksome, heavy and complex powering implements beset by their own inherent vagaries. It follows that these several limitations have enlarged the initial difficulties of attaining a relatively high gyroscopic sensitivity and accuracy. It will also be apparent that the operational lifespans of the devices are inherently limited with the introduced complexities. Further, fluid gyros heretofore have been difiicult to develop into more desirable miniaturized dimension, a problem particularly in evidence where fluid drive systems must be attached to the annular fluid raceway. The fluid spinning mass gyros have been seen to utilize damping schemes identical or similar to those incorporated within conventional gyros, thereby offering no improvement in that technical sphere.

Similarly, the fluid gyros offered to industry have utilized, without particular improvement or new result, conventional readout or pick-off systems from which their outputs are factored into related user or control systems. Consequently, the design choice of a fluid approach has not been promoted by a realistic contribution or improvement within this discipline. The aircraft industry, for example, will find ready application of a sensitive fluid rate gyro in combination with an integral fluidic pick-off system. An increased emphasis by that industry in developing high speed and high performance aircraft operable within expanded flight envelopes and under extreme weather conditions has required new approaches to vehicle handling schemes. The newly imposed flight characteristics have resulted in insufiiciencies in inherent damping in relation to the available control power. As a result, pilot anticipatory response requirements have been considerably increased. At present, airborne flight control systems employ complex stability augmentation, fly-bywire, or control stick steering and open loop damping. These control arrangements are characterized by lower usable lifespans, lower reliability and high maintenance requirements, consequently, their replacement by a less complex and more reliable augmentation system would be highly desirable.

SUMMARY OF THE INVENTION The inventive gyroscope now presented offers solution to the deficiencies, drawbacks and operational problems outlined above by providing, inter alia, a spinning fluid mass gyroscopic system which, while retaining requisite high sensitivity and accuracy, is amenable to simple, efficient and, consequently, inexpensive design approaches. The system of the invention, characterized in utilizing fluid dynamics principles to produce a spinning body or mass of rotating liquid, is capable of operation with a broad spectrum of fluids, ranging from those of very high density such as mercury to those having an advantageously light unit weight.

In the present system, fluid is caused to rotate within a toroidal container or annular confinement device which itself is immersed within the fluid media. The torus or annular raceway utilized with the inventive concept is characterized in its acting as a temporary trap or capacitor for the angular momentum of a continuously injected and relatively modest fluid flow input. The configuration of the torus or annular confinement device is unusual by virtue of its not being completely closed to define a fluid raceway, as distinguished from devices heretofore introduced. By contrast, the submerged torus of the invention is fashioned having a slot disposed along its inner central periphery through which the fluid of the system is free to pass. Numerous advantageous characteristics will be seen to be derived from this unique arrangement, which among others, may be highlighted as follows:

Inasmuch as a slotted raceway is incorporated within the system, a simple fluid nozzle arrangement may be used for the purpose of imparting a given velocity to the fluid mass spinning within the raceway. Of particular consequence, these nozzles need not in any way be physically supported by the annular raceway. As a result, the earlier discussed depredations flowing from the use and suspension of magnetohydrodynamic pumps upon and over the raceway are eliminated. Further, the use of a liquid metal as the pumped fluid media necessary to the functioning of such pumps is no longer required.

The slotted annular raceway of the instant invention is mounted in a manner immersing it within the fluid medium utilized for establishing a spinning mass. As a result of this immersion, unwanted random oscillations which might otherwise be encountered in consequence of the turbulence developing from a spinning fluid are effectively dampened. This inherent damping characteristic minimizes or eliminates the necessity for mounting with the gyro any of the many varieties of expense contributing mechanica damping systems commonly observed in the industry.

The self-damping characteristics of the gyro are also seen to provide a secondary advantage. By virtue of the immersed raceway geometry, there results a desirably low noise level and enhanced resistance of the gyro suspended assembly to externally derived shock forces. Overall gyroscopic performance under a widened variety of applications is improved thereby.

A broad selection of fluids are available for use with the present device, including fluids which are noncorrosive and nonmetallic or not affected by magnetic fields. By avoiding the necessity of using the latter liquid metals and the like, spurious torques which might otherwise be induced through an ambient environment or contiguous machinery are eliminated. In addition to avoiding the considerable complexities of supplying power to a rotating liquid metal encapsulated within a closed channel spinning circuit, there is also avoided the need for providing a separate cooling of the gyro structure in order to dissipate heat which is generated by such an arrangement. This heat development has been considered to be generated by such phenomena as wall friction, by the decay of unavoidable turbulence in the rotating liquid metal fluid and by energy losses emanating from within the circulating pump mechanism. As an added design advantage in this regard, fluids available for use within the overall system may have a low thermal conductivity.

It may be noted further that the gyroscope of the present invention is not compelled to re-work or continue to circulate within the annular raceway the same identifiable quantum of spinning fluid. To the contrary, the instant device retains the capability of introducing a continuing supply of fluid into both its annular raceway and its suspending media. This universal fluid characteristic renders the unit easily adaptable to intimate association within pure fluid or fluidic control systems and the like. When so associated within a fluidic system, there exists little or no necessity for the introduction of interface transponder signal transferring devices.

The design flexibility resulting from the mere optional use of such interface devices opens the gyro of the present invention to a much broader spectrum of technical utilization. As one example, angular rate gyros fabricated in accordance with the present invention are capable of intimate incorporation within the hydraulic control system of a modern, high performance aircraft to provide a fluidic stability augmentation system. A rate feedback generated from the gyros may be used to assist a pilot by sensing the rate of change of vehicle attitude and reacting to introduce a control lead. By using the relatively inexpensive and rugged gyro system of the invention, a considerable simplification of the problem of developing an adequate solution to the earlier discussed pilot anticipatory response problem may be provided.

A further object of the invention is to provide a rate gyro operating on fluid dynamic principles to produce a spinning fluid mass, the gyro being fabricable at relatively low cost while remaining adequately sensitive and reliable, and being usable in a servo made to stabilize one axis of an inertial platform, or in an angular made to measure spatial movement from a reference datum.

Further advantages and objectives of the present gyro will become apparent from the following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially schematic and sectional representation of a rate gyro constructed in accordance with the invention showing nozzle configuration and fluid directional flow.

FIG. 2 is a perspective view of a rate gyro constructed in accordance with the invention with portions cut away to reveal internal structure.

FIG. 3 is an elevational view taken along the vertical section of line 3--3 of FIG. 2.

FIG. 4 is a sectional view taken along the vertical section through line 4-4 of FIG. 3.

FIG. 5 is a partial sectional view taken along the line 55 of FIG. 4.

FIG. 6 is a diagrammatic representation of the pick-off system of the embodiment of the invention described herein.

FIG. 7 is a theoretical representation showing computational symbols utilized in the present description of a preferred embodiment.

FIG. 8 also is a theoretical representation of computational symbols used in describing the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In physical principle, the gyroscope of the invention causes the spinning of a mass of fluid to evoke a stable mode. Fluid used with the arrangement is constrained within a requisite annular path by a container or raceway. The container, however, is not completely closed but has an opening in the form of a circumferential slot along its inward side. As such, the raceway serves as a temporary trap or capacitor for the angular momentum of a continuously injected fluid flow. Depending upon the dimensions desired, this fluid flow may be relatively modest. The container or raceway is submerged within a body of the circulating fluid and, as such, inherently tends to damp the random oscillations encountered from any internal turbulence. From this basic arrangement, it will be apparent that numerous fluid gyroscopic applications are available, particularly those providing a rate integrating gyro having a single axis of freedom. Rate gyros may be designed for use in a servo mode'for the purpose of stabilizing one axis of an inertial platform, or in an angular mode to measure or reflect spatial movement from a reference datum.

In the embodiment now described, a rate gyro is used in an angular mode. The responses deriving from angular rate gyros are generally detected for measurement by either of two systems. In both systems the axis of rotation of the spinning mass is restrained by one or two calibrated torsion springs having a common axis normal to the rotor raceway axis. Thusly suspended, the rotor axis can tilt only about the spring axis. Should the suspended operative rotor then be subjected to an imposed angular velocity about a third axis normal to the two preceding ones, a gyroscopic torque is developed within the suspending springs about their common axis. This torque, and therefore the imposed angular velocity, is then measured. In one conventional torque measuring arrangement the gyro rotor is permitted to tilt with the imposed rate until the torque of the springs equals the torque imposed gyroscopically, and the resulting angle of tilt is measured for conversion by known analytical procedures to convenient data quantities. This system is referred to as a direct read-out mode.

In a second system the gyro rotor is restrained such that its tilt about the suspending axis is held substantially at zero. The restraint requisite to maintaining a non-tilting status is generated by a feed-back servo assembly which develops a torque upon the gyro rotor axis of a magnitude always equal and opposite to the gyroscopic torque. For this case, the load on the servo-system provides an output signal by means of which the imposed angular velocity may be measured by conventional techniques. The latter system is commonly referred to as a null method read out.

In the embodiment now described, the former direct read-out mode of operation will be seen to be used.

General structure Referring to FIG. 1, a schematic representation of the raceway of a fluid rate gyro is provided for the purpose of more clearly illustrating fluid movement evolved with the inventive arrangement. In the figure, an annular raceway 2 which may be shaped in the form of a torus is suspended along one axis to the generally indicated fixed mounting points of an inertial platform ll. Attachment is provided by interconnecting torsion restraint bars 3 and 4 which are calibrated to reflect an imposed angular rate as is discussed in connection with later figures. Fluid is introduced into raceway 2 through an injection device which is independently suspended from the inertial platformand which terminates in dual geometrically symmetrical nozzles 5. As may be evidenced from the drawing, fluid is introduced into the nozzles 5 from a supporting stem or the like at the manifold portion 6. The manifold-nozzle assembly is preferably designed and fabricated for low internal frictional drag and consequent improved efliciency by providing a relatively higher cross-section at the manifold portion 6 which progressively diminishes toward the nozzle outlets. Upon issuing with a particular momentum from the nozzles 5, as is represented by the arrows, the fluid spins about the raceway to establish a rotating fluid rotor. Inasmuch as the nozzle structure 51 is itself immersed within the spinning fluid stream, it may be found desirable to improve rotor flow efliciency by imparting an external oval shape to it thereby presenting a stream-lined cross-section to the already rotating fluid.

Fluid is permitted to exit from the raceway at slots such as shown at 7 disposed about its inner periphery. Since the raceway is immersed, the fluid so exiting joins in providing buoyant support and damping for the assembly. It is preferred that the slots 7 be dimensioned to permit the egress of that portion of fluid which has, at a given point in time, surrendered its initial nozzle momentum and consequent velocity to frictional losses encountered in the course of traversing the raceway. In the same vein, fluid ingressing from the nozzles, continually replaces that lost momentum and fluid. By thusly limiting the dimensions of the slots, a higher degree or quality of fluid rotational directing may be realized to enhance gyroscopic performance.

A pick-off system for the device is shown generally in block form at 8. This system may be designed from a variety of technical approaches, one of which is thoroughly discussed in connection with later figures.

Turning to FIGS. 2 and 3, a particular embodiment of a fluid rate gyro in accordance with the invention is shown mounted upon a planar inertial platform or base 10. The entire gyro assembly is encapsulated within a canopy 11 attached in fluid tight connection to the upper surface of platform along the flaired edge 13. Upon the upper face of the platform there is disposed a torus shaped annular raceway shown generally at 12. The torus 12, serving as an angular momentum housing, is hollow, having a circular internal cross-section as is seen at 14.

Additionally formed within the. torus is a continuous slot extending around its inner periphery and aligned symmetrically with its transverse axis. As discussed in connection with FIG. 1, the slot need not be continuous. Depending outwardly along a common transverse axis of the torus are mounting nodules 16 and 18. The torus 12 and nodules 16 and 18 are fashioned for convenience in mating halves from a material such as styrofoam selected so as to render the unit as neutrally buoyant as possible within its intended surrounding fluid medium. The rounded walls of the internal portion 14 of the torus are preferably formed so as to present as smooth a surface as practicable to fluids spinning therein. For purposes of improving fluid directional flow and minimizing any turbulence developed within the torus, fluid baflles may also be positioned within the torus interior 14.

Small assembling brackets such as that depicted at 20 as well as tongue and groove connectors 22 may be molded with the twin torus halves in order to facilitate their union following fabrication as by molding or the like. A torus shape for the raceway 12 is preferred for the presently described embodiment of the gyro. However, it will be apparent that annular raceways having other than rounded internal cross-sections may be adaptable to the inventive concept. The particular selection of cross section for each application of the gyro will be made in light of the ultimate sensitivity and internal fluid turbulence characteristics demanded by a given set of design criteria.

The torus is axially suspended through its respective mounting nodules 16 and 18 to oppositely disposed torsion mount structures shown generally at 24 and 26. These structures are dimensioned and positioned so as to both hold the torus in proper station with respect to fluid input and to grip one end of the torsion restraint bars 28 and 30 fixed respectively to nodules 16 and 18. The torsion bars 28 and 30 are machined having a flanged portion for ready attachment to the outer faces of the mounting nodules along with necked down portions respectively at 32 and 34. Torsion bar 28 terminates in a circular end flange portion 33 which is, in turn, removably, but securely gripped by a cap 36 mounted upon pier 38 of the torsion mount structure 24. Compressive gripping of the flange through the cap is provided by machine bolts as at 40. Similarly, torsion bar 30 terminates in a circular end flange portion which is, in turn, removably but securely gripped by a cap 42 mounted upon an adjustable mounting bracket 44. A machine bolt 46 retains the cap 42 compressively against the torsion bar flange 35. The mounting bracket 44 is held in selected vertical position by a machine screw 46 threadedly engaging a corresponding tapped bore within pier 48 of the torsion mount structure 26. Screw 46 is seen to nest within a counterbore in bracket 44, its shank extending, in turn, through an elongate slot situated inwardly of the recess. It will be apparent that'the above-described conventional assembly will allow for manual vertical adjustment of the T-shaped mounting bracket 44. Bracket 44 is retained in an alignment perpendicular to the base 10 by guide members 50 and 52 attached by machine screws to the outward face of pier 48. These U-shapcd members provide two knife edge contacts at either side of the elongate stem of T- shaped mounting bracket 44. To facilitate precise vertical adjustment, an internally wrenched machine screw 54 extends into a tapped bore within the platform 10 and protrudes therethrough at 56 to abut against the underside of bracket 44.

It will be apparent to those skilled in the art that the cross-sectional dimension as well as materials choice for the torsion bars 28 and 30 are of considerable importance in determining the imposed rate output values of the gyro. Their dimension and corresponding values of torsional resistance will be factored into the mathematical model of the rate gyro.

Turning now to the power or fluid input supply to the rate gyro, pressurized fluid is introduced into the torus shaped raceway through two fluid rotor feed nozzles and conduits at 58 and 60. The simple nozzles are formed at the termini of two conduits having a semi-circular shape and are aligned to direct the output fluid flow tangentially along the inner surface of the raceway 12. The nozzle conduits extend horizontally from the raceway interior 14 and are attached in fluid communication with a hexagonal manifold 62. As discussed earlier in connection with FIG. 1, a preferred, more eflicient nozzle design will evidence a gradually diminishing conduit cross-section coupled with an external streamlined shape. Manifold 62 is threaded or soldered to a short cylindrical spacer 64 which, in turn is held in position by a common union 66. Union 66 is threadedly attached to a pipe or conduit 68 which, in turn, is threaded into a tapped bore 70 extending through the platform 10. A lock nut 72 secures the entire fluid input assembly against the platform 10. Fluid input means (not shown) are attached to the underside of the platform by conventional fluid coupling methods. Additionally extending through the platform 10 is a fluid outlet port 74 which is also tapped for attachment to lead-01f conduiting.

An important aspect of the present invention resides in the independent suspension of the fluid input nozzles 58 and 60. By virtue of their platform mounted support, the raceway 12 is afforded a greatly improved suspension arrangement over the inertial platform. The latter suspension design need not accommodate weight and spurious moment contributing driving devices. Further, the torsion restraint bars 28 and 30 may be made solid thereby aflording greater design breadth to the system. By contrast, should hollow torsion members be necessitated in order to introduce powering fluid into the raceway, the rate gyro designer would be limited to the selection of a much stiffer and consequently, undesirable method of suspension-The latter consequence would result in a more restrictive gyroscopic sensitivity. It will also be apparent that the number of fluid input nozzles utilized may be varied to suit a given set of design criteria. Additionally, the positioning of the nozzles within the interior 14 of the raceway is a matter of design choice. Generally, it has been found desirable to arrange the geometry of nozzles 58 and 60 as well as the dimension of the peripheral slot so as to approach as near as practicable to a zero fluid income or outgo velocity at the slot opening; that is, there should only be just enough fluid flow through the device to compensate the internal energy losses and to sustain the desired level of angular momentum of the trapped fluid flow in the raceway 12. The latter adjustment is considered to abate internally generated noise. In the same regard, the fluid outlet port is preferably made having a relatively large cross-section, it being theoretically desirable to maintain fluid pressure within the canopy 11 encapsulation as low as possible.

Pick-01f system structure I The pick-01f or imposed rate detection system selected for the instant embodyment of the invention is illustrated in connection with FIGS. 4, 5 and 6. Where appropriate, the same reference numerals as are employed in the earlier figures are interposed within the theoretical schematic diagram of FIG. 6 in the interest of clarity. The direct read-out system incorporated with the embodyment employs a displacement arm which is fixed to nodule 18 of the raceway 12. Note that the entire pick-off system is submerged with the earlier described gyro assembly beneath the canopy 11.

As has been herein pointed out, the raceway 12 or angular momentum trap will precess in reaction to the tional to the input rate if the restraining torques are linear. In the present arrangement the displacement of the raceway is determined by the effect of movement of the displacement arm 80 toward or away from two fluid output nozzles 82 and 84 positioned respectively beneath the lower surface of each of its ends. These nozzles supply a continuing fluid flow against the underside of the leg of each arm and are, in turn, interconnected within a conventional fluidic bridge circuit as depicted in FIG. and incorporated within the pier 48.

Fluid under pressure is supplied into both nozzles 82 and 84 from a common input supply port 86 situated in the platform and tapped to receive an appropriately insertable coupling. From the port 86, the fluid enters a vertical channel 88 bored into the bottom surface of pier 48 and extending up to about its middle. At about the midpoint of pier 48, the sensing fluid is introduced into a horizontal cross channel 90. The cross channel 90 delivers pressurized fluid to each side of the pier 48 for entry within longitudinally and horizontally disposed bores 92 and 94. Cross channel 90 is closed from ambient fluid within the encapsulated canopy by the simple expedient of a machine screw and gasket assembly 96 situated at one side of pier 48. Parallel bores 92 and 94 are identical in structure and are fitted to initially present a filter as at 98 in bore 92 to the incoming fluid from cross channel 90. The selection of filter will be dependent upon such parameters as fluid viscosity and the propensity for contaminants to enter the overall fluid system. Upon coursing through the filters as at 98, the fluid is presented to a first disk-shaped orifice 100 fitted within a counterbore by an O-ring gasket or the like 102. From orifice 100 the fluid enters a second counterbore providing a cavity as at 104 from which the fluid may enter a second vertical leg. The fluid is restricted from further movement through the bore 92 by a disk-shaped stopper 106 having an O-ring gasket or the like 108 disposed within a groove within its outer periphery. Stopper 106 is, in turn, remov-' and conduit 120 within bore 94, or, alternately, the fluid progresses upwardly to the nozzles 82 and 84 through a conduit formed within the same bore. These latter nozzle delivery conduits are illustrated at 122 and 124. At the upward portion of pier 48, vertical conduits 122 and 124 intersect parallel, horizontal conduits 126 and 128 which serve to redirect the fluid into respective nozzles 82 and 84. As will be elaborated upon more fully hereinafter, the diameter of nozzles 82 and 84 is designed as less than that of the orifices 100. Each of the nozzles 82 and 84 are either press fitted or brazed within counterbores respectively formed in conduits 122 and 124 from the top surface of pier 48.

Returning to the output differential pressure conduits 118 and 120, they are seen to terminate respectively in Theory of operatiorrangular momentum trap A broadened application of control or sensing devices such as the rate gyro described above is somewhat dependent upon their mathematical predictability. Accordingly, a transfer function approach for the device is now 10 outlined in the interest of a more complete disclosure of the inventive concept. Referring to FIG. 7, a schematic aid for showing directional and vector symbolism is presented. The figure shows an angular momentum trap retaining a spinning fluid caused to precess as a result of an input angular rate. The resultant force produces a torque Tq at the restraining torsion bars. This torque will be proportional to the input angle rate 0: as given by the ex ression:

Tq=Hw 1) where:

H =angular momenturn=I S2 where I spinning fluid inertia and Q=the effective angular velocity of the rotor The torque Tq is opposed by three restraints: (a) Inertia or I,&

Where I, is the spinning fluids moment of inertia about the 9 axis and H is the corresponding angular acceleration;

or, assuming 0 to be in the form Ae where A is amplitude at 2:0 and the real part of S provides the damping factor (e and the imaginary part gives the frequency of oscillation, then:

the spinning fluids moment of inertia about the 0 axis contains two moments:

(a) That of the fluid rotor about the 0 axis, or

and

(b) A virtual movement of inertia which is due to the rotor housing revolving within the encapsulating fluid. This approach is fully described in the publication: Hydrodynamics, by H. Lamb, Dover Publications, sixth edition,

1932, section 121 at pages 163 and 164. Combining the aforedisclosed moments of inertia, there results:

I=Iv+IR From the Hydrodynamics reference, supra,

has been determined to be:

IV6=16/14pr (9) where =the mass density of the surrounding fluid and r=the radius of the fluid rotor case assuming a disk shape. (See FIG. 8.)

Substituting from Equation 7:

Hw=[(IV+IR)S +,BS+ I016 (10) and the general transfer function for the gyro becomes Displacement pick-off equation An equation for the differential pressure AP existing between nozzles 82 and 84, or P -P in the branch diagram of FIG. 5 is discussed in the publication Hydraulic Servo Control Valves, by Axelroad et al., parts 1 through 5, WADC Technical Report 5 5-59, August 1958. Utilizing the discussion of the reference, differential pressure across the circuit can be .determined as:

(as) l fbdfli tfl tfl P =supply pressure P =drain pressure h=the gap initially set between the nozzles 82 and 84 and cross arm 80 r=the ratio of the orifice coeflicient of the nozzles over that of orifice 100 x=the increment of movement of the cross arm toward or away from a nozzle As may be evidenced from the foregoing, a mathematical model may be derived for both the basic concept and typical pick-off systems incorporated with it. The availability of such models provides some insight into the broad scope of uses to which the inventive gyro may be adapted.

While there have been shown and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions in the form of detail of the gyro shown and its method of manufacture may be made by those skilled in the art without departing from the spirit of the invention.

We claim:

1. An inertial device responsive to movement comprising in combination:

(a) Containment means for enveloping a body of transient fluid, a hollow annular raceway neutrally buoyant within the body of fluid and adapted to direct fluid to flow in an annular path disposed within said containment means and having an open portion situate inwardly from its outer periphery for permitting the egress and ingress of said fluid from and into said raceway;

(b) Fluid injection means adapted to introduce a moving fluid tangentially along the outward internal surface of said annular raceway; and

() Outlet means for permitting the egress of fluid from said containment means.

2. An inertial device responsive to movement comprising in combination:

(a) Containment means for enveloping a body of transient fluid, a hollow'annular raceway adapted to direct fluid to flow in an annular path disposed within said containment means and having an open portion situate inwardly from its outer periphery for permitting the egress and ingress of said fluid from and into said raceway;

(b) Fluid injection means adapted to introduce a moving fluid tangentially along the outward internal surface of said annular raceway;

(c) Outlet means for permitting the egress of fluid from said containment means; and

(d) Said open portion of said hollow annular raceway being dimensioned in a manner permitting the velocities of said ingressing and egressing fluid to approach near to zero.

3. An inertial device responsive to movement comprising in combination:

(a) Containment means, mounted upon an inertial platform, for enveloping a body of transient fluid, a hollow annular raceway adapted to direct fluid to flow in an annular path disposed within said containment means and having an open portion situate inwardly from its outer periphery for permitting the egress and ingress of said fluid from and into said raceway;

( b) Fluid injection means adapted to introduce a moving fluid tangentially along the outward internal sur- Where face of said annular raceway including at least one fluid conducting conduit mounted upon said inertial platform and terminating in a nozzle situate within said raceway and remote from the surface thereof; and

(0) Outlet means for permitting the egress of fluid from said containment means.

4. An inertial device responsive to angular movement comprising:

(a) An inertial platform;

(b) Containment-means mounted upon said platform for enveloping a body of transient fluid;

(c) A hollow annular raceway, adapted to direct fluid to flow in an annular path, disposed within said containment means and having a continuous annular slot situate inwardly from its outer periphery for permitting said fluid to move from and into said annular path;

(d) Fluid injection means adapted to introduce a moving fluid tangentially along the outward internal surface of said annular raceway;

(e), Supporting means in connection with said inertial platform for suspending said annular raceway in cooperative relationship with said inertial platform; and

(f) Outlet means for permitting the egress of fluid from said containment means.

5. An inertial device responsive to angular movement comprising:

(a) An inertial platform;

(b) Containment means mounted upon said platform for enveloping a body of transient fluid;

(c) A hollow annular raceway, adapted to direct fluid to flow in an annular path, disposed within said containment means and having an open portion situate inwardly from its outer periphery for permitting said fluid to move from and into said annular path;

(d) Fluid injection means adapted to introduce a moving fluid tangentially along the outward internal surface of said annular raceway;

(e) Supporting means in connection with said inertial platform for suspending said annular raceway in cooperative relationship with said inertial platform, said supporting means including at least one torsion bar having a given torque resistance, spaced intermediate and fixed to said supporting means and said annular raceway and aligned along a diameter of said raceway so as to afford said raceway a one degree freedom of movement; and

(f) Outlet means for permitting the egress of fluid from said containment means.

6. The inertial device of claim 5 in which said torsion bar is solid.

7. The inertial device of claim 5 which includes: sensing means mounted upon said inertial platform and associated with said annular raceway so as to respond proportionately to its movement.

8. The inertial device of claim 5 in which said fluid injection means include at least one fluid conducting conduit mounted upon said inertial platform and terminating in a nozzle situate within said raceway and remote from i the surface thereof, said nozzle being positioned to dis- (c) A hollow annular raceway, adapted to direct fluid to flow in an annular path, disposed within said containment means and having an open portion situate inwardly from its outer periphery for permitting said fluid to move from and into said annular path;

(d) Fluid injection means adapted to introduce a moving fluid tangentially along the outward internal surface of said annular raceway;

(e) Said open portion of said hollow annular raceway being dimensioned so as to permit the egress of that portion of fluid which has, at a given point in time, surrendered its initial nozzle momentum and consequent velocity to frictional losses encountered while traversing the said raceway;

(f) Supporting means in connection with said inertial 15 platform for suspending said annular raceway in cooperative relationship with said inertial platform; and

(g) Outlet means for permitting the egress of fluid from said containment means.

References Cited UNITED STATES PATENTS 2,953,925 9/1960 Yeadon 74-5.7 2,971,384 2/1961 Johnston 745.7 3,162,053 12/1964 Blitz 74-543 XR 3,296,870 1/1967 Turnblade et al 745 XR FRED C. MATTERN, 111., Primary Examiner M. ANTONAKAS, Assistant Examiner US. Cl. X.R. 

